412015-83-9Relevant articles and documents
Synthesis and characterization of amphiphilic silica nanoparticles covered by block copolymers branching photochromic diarylethene moieties on side chain
Seno, Ryuta,Kobatake, Seiya
, p. 166 - 174 (2015)
Silica nanoparticles covered with polystyrene branching diarylethene moieties to the side chains are synthesized by reversible addition-fragmentation chain transfer polymerization on silica nanoparticles. The resulting nanoparticles are soluble in toluene
EPR measurement of fragmentation kinetics in dithiobenzoate-mediated RAFT polymerization
Meiser, Wibke,Barth, Johannes,Buback, Michael,Kattner, Hendrik,Vana, Philipp
experimental part, p. 2474 - 2480 (2012/03/26)
The kinetics of reversible addition-fragmentation chain transfer (RAFT) polymerization of butyl acrylate with ethyl S-thiobenzoyl-2-thiopropionate (ETTP) as the RAFT agent has been studied. The concentrations of propagating (P?) and intermediate radicals (INT?) were measured via highly time-resolved EPR spectroscopy after initiation by a laser single pulse. Predici simulation of experimental data results in rate coefficients for -40 °C of kad = (1.4 ± 0.4) × 106 L mol-1 s-1, kβ = (4.7 ± 1.5) s-1, and ktcross = 0.25 × kt, where kt is the rate coefficient for termination of two P? species. Fast fragmentation of the intermediate radical is thus observed at this low temperature. Measuring the ratio of INT ? to P? concentrations during stationary polymerization at -40 and 70 °C yields Keq = k ad/kβ values of (2.3 ± 0.6) × 10 5 and 75 ± 15 L mol-1, respectively, which correspond to an apparent activation energy difference, EA(k ad/kβ), of -49.5 kJ mol-1.
